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wap writes "The language/VM/religion that everyone loves to hate is now serving another cup: Java 1.5 is ready for download. The new features of 1.5 have been discussed here before. I, for one, welcome our new virtual machine overlord. I have been using the release candidate, and startup times are noticeably faster, as is overall performance, and the new features like typesafe collections and static imports are great to have. Let the Java flames begin!"

Now we just need to be able to build Eclipse itself using Java 1.5. I really really want to use 1.5 in my Eclipse plugins. I want real container classes dammit!:-P

Currently you probably could build Eclipse using 1.5, but the Eclipse release engineering folks are still building using 1.4 (or at least, they were as of a month or so ago, and I haven't seen any mailing list traffic to the contrary). There won't be any official builds of Eclipse done with 1.5 for a while yet I think.

OOP advantage is best seen in large projects. Particullary collaborations. I've worked on large codebase non-OO projects before and know the headaches.

Also, what about compile times and the fact that Java actually doesn't work on all interfaces?

Dunno. What interfaces are you talking about?

Compile times? Java's pretty speedy compiling. Than again, I dont have a 286. Will say this though: Make is a hell of a lot quicker than Ant. Ofcourse you could always use Make for building java though.

(And as a side note, I don't like the fact that you have to type four lines of code to do what C++ could do with a simple cin >> var;

After they took all that time to rewrite it with the latest API they claim they can closely track Sun releases. This will be the first big thing since then, so it will be a test of Apple to get it out quickly.

Apparently it is planned for release with Tiger, the next major release of OSX. I don't know whether it will be available prior to the release of Tiger, if not, it is likely to prevent most developers from coding in it (what is the point in coding in Java if it won't work on the #2 desktop OS?).

... it is likely to prevent most developers from coding in it Not really. CodeGuide, www.omnicore.com, thats an IDE, has a MAc release since years. That allows using Java 1.5 features in coding. And as you can create byte code compatible with JDK 1.4 released software will run on a Mac as well. Tehre are minor issues however e.g. new methods in java.lang.String wich work fine in the IDE (becase the classpath is different) but not in standalone mode. Nevertheless, I'm coding on a Mac, not necessaryly for a Mac, thats why I use java with generics and the later Java 1.5 betas since over 2 years now. (And since about 14 month on a Mac).

I would expect that Eclispe and other major IDE vendors have a Mac version bundled with JDK 1.5 runtime libraries as well.

I downloaded the beta (from where I can't say:-), but it only installs on Tiger (OS X 10.4). Since I don't really want to run a pre-release OS, I took a pass. But JDK 1.5 is coming, it's just several months off.

But by your post, you had probably already guessed that. At least it's probably less than four years, like it was before Mac folks got JDK 1.2...

I like this trend. These, among other changes in version 5, are all steps towards reducing the awkwardness in the Java syntax that many people complain about. Java is a young, evolving language that still has a lot of potential.

It is a bit funny, though, that this evolution takes the form of borrowing stuff from an ancient language. Maybe C just got things right in the first place, huh?

Actually, C/C++ had a lot of good ideas, but it took a while for Java to get them right. The new Generic Types add compile-time typechecking and remove a lot of typecasting without adding a huge amount of complexity to the language like C++ templates do, and without causing multiple copies of the code to be generated. Enums in Java are full-fledged classes of actual objects with methods, unlike in C where they are just markers (they are object constants instead of integer constants; no difference in efficie

Generics in Java have a smaller scope, when compared to C++ templates. The objective in Java is to provide a type-safety mechanism for containers. In C++, it is much more than that. Unfortunately, it is this extra ability in C++ that makes for some really complex code. Not sure if this has already been mentioned in this story, but it has been theorized that C++ templates are themselves turing complete (though I havent seen a proof to that effect).

I'm a bit puzzled by all the generics nay-sayers. I have tried out the feature, and they augment the language. I have yet to see a downside to this feature in Java (unless one counts the inability of the compiler to fully utilize the additional type-safety in compiler error messages). What is all the flap about?

I was actually looking forward to templates in Java but was disappointed once I saw the implementation of generics.

Every cast operation in Java is expensive because the VM invokes security code to verify that the cast is legal. Java generics don't allow you to avoid the implicit cast so you still get the performance hit. Generics only make the code look cleaner.

Template meta-programming is also a very important part of the modern C++ libraries and is also something that generics cannot do.

My apologies for the horrible look of the code samples. Slashdot won't let me use nice, short lines, as it results in lines which are too short. Gah! Apparently I need ~40 characters per line (average) to get past the @#$% filter... This has to be the most annoying filter I've ever come across; I've spent more time getting past the filter than responding to your question!

Iterators are similar to java.util.Iterator. C# iterators are compiler support for implementing the System.Collections.IEnumerator interface. For example, in Java you'd write:

Anonymous Methods are methods without a name, just like Java anonymous classes are classes without a name. Same basic idea, fewer braces. They also act as full closures; while Java requires that all stack variables referenced from an anonymous class be final, C# doesn't require this.

The above example is bad, but you can let your imagination run wild. This is very useful for event handlers.

Partial Types

allow you to split a single class definition across multiple files. This is useful to prevent > 50 KB source files (yech!), and makes it easier to have part of a class machine generated (by a GUI builder) and part hand-written. Some people hate it, others are ambivalent, but it can be handy:

// File a1.cspartial class Foo {public int a;}

// File a2.cspartial class Foo {public int b;}

Nullable types are primarily useful for database support in the.NET type system. DB types can be "nullable" -- not present. For reference types, this is easy -- use null. For.NET value types, this isn't possible, as value types can't be null. The solution is to introduce a generic class System.Nullable<T>, which can wrap value types such as int.

I've been disappointed with IBM's response to Java lately. The last version easily downloaded for Windows is 1.3. The only way I was able to get Java 1.4 for Windows was to download the MQ Series client (like 200MB big!) and pull the JDK out of that...

I wonder if IBM will have a 1.5 JDK? For a company that is putting a lot of juice behind Java, it seems odd that they don't make the JDK available to others...

First off, Websphere 4.0 is J2EE 1.2 only. You need Websphere 5.0 to get to J2EE 1.3.1. In Websphere 5.1, you at least get JDK 1.4, and a few J2EE 1.4 tidbits (JSTL 1.1, for example).

However, your ClassCastExceptions will only get bumped to compile time in JDK 1.5, true. But I must admit that in eight years of Java programming, I've never had this particular problem where it didn't take more than a few seconds to find the source of the bug.

I really just want the metadata stuff (which was obviously ripped off from C#, but it's a great idea). That, and EJB 3.0, which gets rid of the stupid deployment descriptors.

Well, some may call the 1.5 as being increasingly bloatware, but, why in some aspects this may be true, I think all by all there are considerable improvements over the former releases, especially 1.4.2.

JVM 1.4.2 (at least some sub-versions) were riddled with bugs, which, for instance, become apparent when people use systems that rely on it in a special way, as with Freenet. It comes as no surprise, that there were numerous reports of some errors on OSX and BSD, as well as on linux, when running JVM 1.4.2. For some time, we had to say "If you experience any difficulties, please try/revert to JVM 1.4.1 or 1.5.x and see if that solves the problem."

It is crazy to recommend reverting, but the main devls of java were unwilling to remedy the bugs in 1.4.2, claiming it was a Freenet-problem, while our devls said it was a JVM problem. Though it must be said some within freenet claim their is little to no problem with it (probably windows-users, or maybe some sub-versions that worked on specific linux-distributions). Anyway, my advice has always been, and will be (certainly in the light of the stable 1.5 release), to NOT use the 1.4.2, especially when using OSX or another 'nix based OS.

And also; be sure to get the JRE, and not the full SDK, unless you plan to develop Java software.

The new For loop may seem to be just syntactic sugar, but it isn't. It really does make the code look a lot cleaner when you are iterating over a collection or an array. The type safe collections are also very handy--no more class cast exceptions and stuff like that.

It would be nice though if Sun would make Groovy or Jython a standard part of their java distribution. That would definitely make it competitive with.NET

Carrying on down this path much farther, you become able to argue that C is just syntactic sugar for assembly language, and therefore assembly language is just as good.

Actually, except for the standard assumption that
sytactic sugar [wikipedia.org]
be an extension of a core language (and not a completely separate language), it's pretty much true that C is syntactic sugar for assembly language. But syntactic sugar is neither good nor bad in-and-of-itself. If a given instance makes programming easier to do and easier

The new for loop most certainly is syntactic sugar. It's taking something we could do before and shortening it into a new construct.

However, a lot of folks use 'syntactic sugar' as a derisive term. It's not. It saves programmer time. Generally the times that it's bad are when it's (a) hiding what's really happening to a degree that introduces bugs, or (b) misguided, like SQL's attempts at being English-like.

In typical/. style, as soon as Java is as much as mentioned, everybody expects the flame wars to erupt, and they always do...

I try to stay pragmatic about the programming languages that I use. For some jobs, Java would be my last choice, and for some it seems a natural fit. When writing hardware near code, or platform dependant stuff on driver level, nobody in their right mind would attempt to use Java. For high level rapid prototyping, Java is a often a quick and easy way of getting things done.

The biggest problem with Slashdot Java flaming is that people do not realize what Java is.
If you compare language to language, say Java to C, C# or even Ruby and Python, it is easy to see why Java is "slow" and "bloated". But Java is to be compared to something like.NET and not just a language.

Java is a platform. Java provides on-the-fly class loading and verification including digital signing of the code, very fine-grained security model (you can create your own sandbox with whatever security rules you

Nice that Java VM is now faster; it's one of the major drawbacks of java on the desktop. But how does this compare with the new and shiny Mono?
Mono with its distributed system, and if it still beats Java, then java is in for a tough fight.

Sorry, Dude, but the Java VM still is faster than.Net and Mono is significantly slower than.Net (since it is just a basic VM with a basic jit and no runtime optimization)

Despite the having a slower VM, the.Net programs sometimes can be faster than java programs because they are heavily integrated into windows wheras java has to add abstraction layers for not losing portability.

But back to Mono it will probably never be able to catchup speedwise with.Net unless they move to another VM which is main

Over 50% of the.Net libraries have not been ported to Mono and may never be. Mono is pretty cool but until it is fully ported it will remain years behind Java and.Net. You cant compare them like you cant compare java to perl. Java and.Net are very much competitors and will continue to dominate the industry in their niche. Companies need security (as in a future) for their multimillion projects. It took Java ~6 years to self promote. If Mono severely ramps up their efforts, they MIGHT reach the plateau.

Java had all this hype about it when it was promoted nearly a decade ago, but it never got anywhere close to the point where you could walk into your local computer store and buy a major software package that could be run on any platform. I recall that Corel was going to attempt to release a WordPerfect that ran using Java, but that's the most I heard of it being adopted by mainsteam software developers. Does anyone think it will ever take?

What makes you think it hasn't? A single example: What percentage of Apache Foundation products are written in and/or for Java. Note that Apache Foundation products are used extensively in Enterprise software development, deployment and systems.

I honestly wasn't trying to troll. If you walk into a computer store and look at all the off-the shelf consumer-level software products, they're all for Windows. I was hoping that Java would have changed this so that you can buy one of these off-the shelf products and run it on any platform. I know that it has gained acceptance at the enterprise level, I was actually referring to the consumer level.

(i.e. you can't have "-target 1.4 -source 1.5") . Yes, you can have it!But what about your classpath, does it reference the 1.5 JRE? E.g. if the 1.5 java.lang.String gets loaded by an old JVM you might get that errro as well.angel'o'sphere

I would hope that 1.2, 1.3 and 1.4 bytecode would run in the 1.5 JRE. I think it's ambitious to expect 1.5 bytecode to run in a pre-1.5 JRE - the language has new features that such JREs don't know about or support.

While you could obviously write code that interprets 1.5 bytecode so that it will run on a 1.4 JRE, and make it possible to automagically create that code at compile-time, including it by default in the compiled 1.5 code would be wasteful as it's not required to run in a 1.5 environment.

I thought that the compiled Java would remain compatible with the bytecode format used by previous versions.

The bytecode format is still identical. The version number on the file was incremented because classes that depend on assertions could break badly if used on a JVM that doesn't implement them (which is actually a feature of a few classes in java.lang, not a bytecode interpreter feature). Use the '-target' commands recommended by the other posters whenever producing code that doesn't rely on one of the new features.

It has been known for a long time (over a year), that Java programs compiled for 1.5 will not run on a 1.4 VM. However, you can use tools like Retroweaver [sf.net] to get 1.4 compatibility. It rewrites the bytecode of your version 1.5 class files into the 1.4 VM format.

In an interview [sys-con.com] given just last night, the spec lead for 5.0 is asked what in his view the coolest new feature of the language is. Calvin Austin replies: If I just restrict myself to the language it would be metadata (JSR 175). We've only scratched the surface of its potential. For the platform, it's a bytecode insertion for profiling (JSR 163).

One of the new features of Java 1.5 that has not been mentioned much yet is the OpenGL acceleration of Java2D (which underlies Swing and AWT). Adding the flag

-Dsun.java2d.opengl=true

(or by setting the system property in the program) makes pretty much all Java2D calls go directly into OpenGL.

This does indeed work too, I have played around with it and graphically intensive Swing applications really fly with OpenGL activated (given that your graphics card and drivers are sufficiently bug-free and modern). Read about it here [sun.com]

And yes, it does work under Linux, and Windows and Solaris (and most likely will under OS X, though that is up to Apple to implement).

Even without OpenGL acceleration the Swing responsiveness improvements are very impressive, coupled with the much better both default theme and theme mimicking in 1.5 I'd say it is time to retire the Swing troll.

You can't hate any language as much as some people hate Java until it's really reached critical mass.

There are two things that make any really big language a target: 1) people start using it for everything, including things its not suited for. 2) junior folks without a lot of compiler or cross-language experiences will cut their teeth on Java, and at that point in one's career it is sometimes considered cool to blame a bad application's flaws on the language it's written in.

Java has plenty of problems. There are brilliant essays written on it; some of them by Sun engineers. But the complaint linked to in story was so bad by comparison, however, I doin't feel offtopic in addressing some points it raised:

there are a thousand "super-efficient".jar libraries required by a "Hello World" app

No.

it takes 12 objects instantiated in 4 containers to flip a bit in a byte

Oh, I see. You're flipping bytes.

there is the substitution of native performance of compiled code to code compiled "Just Too Late" combined with exceptional memory usage that entails

The VM is more work. Strangely, you will have trouble finding benchmarks that make other comparable high-level languages look way faster than Java on the same _non-user-facing_ application.

As always, code in C, assembler, or another specialized language if you really need to.

The speed thing is well-addressed elsewhere. Enough said for now.

we get the garbage collector which is scientifically fine-tuned to run just when user is expected to interact with the application in most time sensitive manner

People love to bitch about client-side Java. It's as if all the flaws they're used to from other client side systems are fine, because they're used to them, and every foible of Java is worth agonizing over as if it were the worst thing in the world.

I dunno what else to say, but I wrote an enormous graphic-intensive video game in it and it runs fine. And what I did is nothing; somebody cloned the QIII engine to the point where it plays actual Q3A maps (with multiplayer) at respectable framerates.

Once again, someone shows me a shitty client app written by a team of 30 22 year olds in Thailand and claim it's proof that Java sucks. Congratulations.

multiple, insideously incompatible with each other, versions of the so-called "universal" VM

Yes, leaving aside the fact that Microsoft deliberately broke VM compatibility. Not just in one or two big ways. In a lot of little ways. As in on purpose. Great example. Very honest.

There is a giant test suite. Gets better all the time. Reputable VM's pass it. Most of all, though, I just don't run into the cross-VM problem in the first place unless I'm doing 1.1 development for browsers, see above...

We actually abandoned DB2 8.x release because noone could deal with the havoc the DB2 admin tools were causing with various other retarded banking related Java apps.

There we go. The truth outs. You overpaid for a shitty product. Congratulations. You can do that in C or Fortran, too.

As much as I might hate Java, I repeatedly have to throw this one thing into the fray: I had exactly zero former experience with network programming, and still, I was able to produce a basic telnet-like application in under 30 minutes, using only the Java API doc and some logical thinking. And I only had a very brief introduction into the language. Transferring this to C (although the basic structure is exactly the same with BSD and Java sockets) took me about a week, with all those damn low-level error conditions.

And not only was it faster to write in the first place, but the chances are your app will run on Windows out of the box without having to add arbitrary WinSock calls around the place. And it will run on BSD without adding extra network headers and libraries to the makefile after discovering half of them are missing from the default. And it will run on OSX without any knowledge of that platform at all. WORA is indeed real until people try to break it with specifically crafted examples.:-)

Sir, I regret to inform you that you've demonstrated "critical thinking" within a hostile forum. You are no longer allowed to read Slasdot. Move along.

Joking aside, it kills me to see the amount of research and due-diligence that goes into debunking a Microsoft-sponsored benchmark, but when it comes to Java most everyone starts spouting nonsense. People will remember their experiences from 8 years ago, or a bad app, etc. and immediately conclude that Java must suck for every conceivable application.

Java is a tool - no more, no less. Use it where you think it is useful and leave on the shelf if you don't think it will help solve your current problem. Most mature developers know when and where a tool should be applied.

First a disclaimer, I wrote the original post you seem to quote. I do not write Java apps and although I was mostly facetous, here is why I said those things:

there are a thousand "super-efficient".jar libraries required by a "Hello World" app

No.

Well it certainly feels that way when you try to load those apps. They all have excruciating startup times. Perheaps I am wrong and instead they check the integrity of my bank account or weather in China for my convenience. I dont really care, but 5-6 seconds

I will keep repeating ad nauseum that those are the only applications that count to me and many businesses that use them. That is a 100% of a sample of a Java apps that are shitty. Either all of those were written by poeple have no clue what they are doing (unlike all of those wonderful mythical apps always deployed somewhere else and written by enlightened geniuses) or the Java snake oil is just that.

and I am starting to wonder how much experience you have in general, because what I'm conspicuously not hearing is X and Y and Z systems are way better for A and B and C. Just vague generalities about HTML forms and (I think?) coding in C? Or do you perhaps favor VBScript?

Since you are getting more incredibly fanatical and blind by the minute, let me spell it out for you as clear as I can:

For e-commerce, OS/browser agnostic plain HTML on the browser is the only sane way to do anything because it does not rely on any client capablities other then ability to render HTML. No deployment issues, no maintanance costs. Java (and ActiveX and C# and similarly retarded ideas) is a way to create deployment issues and thus support costs and thus employment for countless Java tweaker monkeys. Something dear to your heart no doubt.

For applications that must run on thick-clients (I sure hope due to CPU usage because any other reason in a corporation is plain retarded) one can use native code just fine because: vast majority if C or C++ or any other language programs need only to support very few platforms in their entire life span and the effort to optimize that program for these platforms is well paid for by removal of integration and thus support issues. But such need is extremely rare because vast majority never leave a single platform. A Windows Java app will never run as well as a native Windows app neither will unix Java app run as well as a native unix app. This is not even up for discussion. The most convoluted of JITs and what nots are still overhead over native code and I will not even entertain any moronic discussion on that topic no more that I will entertain discussions of how you can make 2 and 2 equal 7.

I regret to inform you that you are full of shit.

I regret to inform you that you are just a priest of yet another silly language who has no clue who pays his bills. VB apps are everywhere in business, far more so then Java ones. These numbers are representing current jobs, corresponding to a peak in a cycle of a fad, VB waning hard (previous fad), Java peaking (current fad) and C# just coming up. I am fully expecting to have this very same retarded conversation with a C# priest, in, oh about 4 years time.

You sound confused. Are you saying it's easier or cheaper to write native applications? That natives are more secure?
Are you happy with all your current native applications?

No it is you who is utterly confused, something about a theory whereby the Earth is flat and supported by Java beans. To spell it out for you again (I will resist an urge to use large letters): Native apps are easier to write (many decades of experience and tools), run better (many decades of OS design and integration of apps with the OS), cheaper to write and support because they use proven framework and tools, they integrate well with the user environment, have better performance (even the not so well written ones) and the so called "write once, deploy everywhere" is not only unnecessary but is more accurately described as "write once, debug and crash everywhere". Are they more secure? Depends what kind. The "no client side, java-less, HTML only e-commerce"? Most certainly. The locally deployed, locally networking native apps? They are not any more vulnerable then the OS itself. Are we clear now, Your Beanness?

nobody sees the world ending but you, all those students and professors, all those magazines and newswpapers and Fortune 500 compan

I work on a minor, highly targetted Linux distribution. I'd love to include Java, and I actually get a lot of requests for it. But, here's an excerpt from the license agreement you'll find if you look to download the software:

B. License to Distribute Software. Subject to the terms and
conditions of this Agreement and restrictions and
exceptions set forth in the Software README file,
including, but not limited to the Java Technology
Restrictions of these Supplemental Terms, Sun grants you a
non-exclusive, non-transferable, limited license without
fees to reproduce and distribute the Software, provided
that (i) you distribute the Software complete and
unmodified and only bundled as part of, and for the sole
purpose of running, your Programs, (ii) the Programs add
significant and primary functionality to the Software,
(iii) you do not distribute additional software intended to
replace any component(s) of the Software, (iv) you do not
remove or alter any proprietary legends or notices
contained in the Software, (v) you only distribute the
Software subject to a license agreement that protects Sun's
interests consistent with the terms contained in this
Agreement, and (vi) you agree to defend and indemnify Sun
and its licensors from and

(Yes, it really does just end abruptly without finishing the sentence. That trailing "and" there doesn't lead into the next section; it's just not done. Obviously I'm the only one who bothers to read these things -- *including* the people at Sun. Anyway....)

My wish to give the software to my users fails almost every test....

i: I don't want to distribute it for the "sole purpose of running [my] Programs". I want to distribute it so people can run other people's programs, including possibly their own.

iii: oops, I include gcc, which has a Java compiler. And I'm definitely not going to drop that.

iv: ahh, now this one I can agree with -- fine keep your copyright notices, etc.

v: my distribution as a whole is under the GPL. I'd have to run this by our lawyers, but this looks like it'd conflict by requring additional restrictions (even if I could get special dispensation to deal with the other issues).

vi: I don't really have the resources to defend and indemnify Sun "from and", even if I wanted to, thanks.

And frankly, that's why I wish people would stop writing things in Java. It's a pain to deal with. I want to make everything as slick, integrated, and as easy as possible for my end users. Sun makes that impossible for Java applications. If you want your code to be easily integrated and made available to users like mine -- and really, that's users of any Linux distro targetted more broadly than the super-geek sector -- please don't use Java. If you must, at least design it to work with gcj instead of Sun's virtual machine.

Unless Sun changes the license terms, their Java can never fill the "write once, run anywhere" goal -- but cleanly written source in an open language can.

Bah, each new release I try hoping they'll do something about the speed since I like the language better than c/c++.

Since 1.0 there have been three major speed holdbacks preventing me and many others from adopting java:

1) array access too slow due to boundary checking (no, their optimizer doesn't work for my cases, and this is a problem a lot of scientists/performance hungry people have).

#1 has some good solutions on 64-bit platforms developed at the university of georgia, but sun won't include them, nor will they enable a flag on the jvm to turn of bounds checks. GCJ lets you do it, but can't compile everything I need yet.

2) casting raw memory to objects requires a copy. Java needs a structured object without a header to overcome this, such as the struct proposal, which is in the top 25 rfe's yet has no comment from sun.

#2 has a well understood solution that sun is apparently too lazy to even consider implementing.

3) No way to do fast 2d/3d rendered graphics. Too many call overheads & copies.

Sun needs to ditch AWT/Swing, and probably needs to open source java to overcome this. They've proven their inability to keep up a reasonable mapping to modern featuresets.

I'm probably going to have to give up and learn c# since I'd like a more modern language with good tools, but java just doesn't have the speed.

Java should never have memory leaks...All the memory managment should be done by the VM as far as I know...unless there is some advanced stuff i'm just not aware of?

Not memory leaks as such, but "memory leaks" for all practical purposes. How? Well, if you forget to nullify references to objects you no longer use, the garbage collector obviously cannot reclaim that memory..

As far as I'm aware, I don't think your entire app is supposed to be in main(). I normally don't ever nullify references, but my code is modular enough, (i.e. not all in main()) that objects go out of scope when they are no longer needed. This is one of the most ridiculous examples of a straw man argument I have seen.

However, you are quite correct. It can be quite difficult at times to ensure that all objects are correctly cleaned up after usage. As soon as you introduce items such as HashMaps, etc, you run into potential for these problems.

We once had this issue when we embedded the mozilla javascript interpreter in our app. The problem was that you have to create a scope object, with all sorts of predefined classes and functions and so forth. This was expensive, so we pooled them. Unfortunately this left a memory leak, as objects declared in scope by the javascript itself would not tidy up at the end of processing.

Indeed it turns out the library has parent scopes, so we could create a new child scope cheaply each time, but the point remains.

I ran into a fabulous memory leak just last week thanks to Sun. I wrote a client that was accepting messages and persisting them using ObjectOutputStream [sun.com]. I persisted about 40,000 HashMaps, and next thing, my client was using 200M. I wasn't building any lists of the messages, so I was stumped, and I broke out the profiler.

I was surprised to find that the ObjectOutputStream has a static HandleTable inside it that creates an entry for each HashMap that I put through, and it keeps a reference to each HashMap. I searched around, and this is a common problem [utwente.nl] that is not mentioned at all in the javadocs. You're supposed to reset [sun.com]
the ObjectOutputStream periodically to free up the HandleTable. I had assumed that reset was like InputStream's reset [sun.com] and never would have guessed that it had to do with Object caching in the stream.

Also, I don't know for sure, but would what happen if two objects referenced each other but nothing else referenced them. Would gc know to follow the links between the two and see that nothing in the main app is using them?

Yes, Java's GC would notice that nothing is referring to them and remove the objects. This unlike a simple reference counting gc such as python's which would not notice this. Java's GC can even relocate memory on the fly to minimize page misses and avoid memory fragmentation.

Yes, Java's GC would notice that nothing is referring to them and remove the objects. This unlike a simple reference counting gc such as python's which would not notice this. Java's GC can even relocate memory on the fly to minimize page misses and avoid memory fragmentation.

Python actually uses a generational garbage collection system that can break cycles to reclaim unused objects. It also performs certain optimizations to avoid unnecessary memory allocations and deallocations.

All it takes is one pointer *ahem* reference to some object that contanis a reference to another, that contains an array... If you've got a few hashes and arrays in the way, it may be difficult to tell exactly where memory is being used, thus memory leaks.

Well, for a GC that is not difficult to tell at all. Not harder as for a human:DIn C++ somewhere somehow one had called delete. So at the point where in Java a hughe amount of memeory is referenced, and probably never used again, you have a dangling pointer in C++.

but would what happen if two objects referenced each other but nothing else referenced them. Would gc know to follow the links between the two and see that nothing in the main app is using them?

Of course, thats the point about garbage collection:-D

If you have a memory leak in java then it comes from things like that:

Actually no, it is an app problem.
Sun has introduced weak references way back in 1.3 to cope with that problem. And I have to admit, I never had any of these problems since 1.3
But it also could be that your program simply needs a tad more ram.
Following, check out the -Xmx and -Xms parameters of your application startup file and add more ram (java fetches 32MB in without any params and fills it up before it starts the GC for the first time)
That might help.
But never count memory leaks out, they are very rare, but can happen if somebody has tangling references, pretty much the only case where the Garbage Collector can do basically nothing.
The VM itself is not flakey, I have a few servers running here, with an uptime of a year already.

That's not interesting, that's cliche. People have been saying that for years. Let's be honest: virtual machines are where business code is going, and business code (enterprise applications, server side stuff, etc) is the primary focus of Java these days..NET is a clear indication that this trend is a real one, and that that's where the industry is heading.

No, I don't think you should write ls or grep in Java. However, I'd say that you also shouldn't be writing an invoice processing system in C or C ++.

I agree though, the naming of Java is consistently confusing. Should I upgrade from Java 2.. err.. J2SE.. err.. Java 1.3.1_08 to Java 5 or to Java 1.5 or indeed Java 1.5.0. Oh, and is J2EE 1.4 compatible with this new one?

No Hjelfsberg is totally right. The extensions are syntactic sugar. But still they are useful, because, you gain coding efficiency that way.
Autoboxing, foreach, generics are all implemented in a way not to break the byte format, but you still need less code for doing jobs like iterating lists fetching elements from data structures and so on. Day to day stuff which you used every 10th line or os.

Priority #1 for Sun was not to break the bytecode format.
Priority #2 was to ease the life of programmers

The only thing which really will make a difference on code generation level will be the meta data, this one will make life easier for the implementors and for the users of servers. Soap instantly comes to my mind with the C# like @webmethod metadata. No more post and precompilers for doing that stuff, yiehaa.

Hjelfsberg is a smart guy, although I dont share his views on unmanaged exceptions, he is dead right with his comment on this.

If you like C#, VB and.NET that's fine. Unfortunately MS's revenue stream requires that they change your environment on a regular basis. In my opinion that's the worst thing in the world for professional developers. Proficiency comes with experience and if you shift the syntax and grammer around on me every couple of years it's pretty hard to get really good at anything. At least Java is, pretty much, the same now as it's always been for near

I've opted to reply to this rather than mod.
While I think "write-once, run-anywhere" is a bit of a misnomer, it does actually live up to the hype, imho.

You can't really appreciate it however, until you've spent weeks porting C code between platforms, and a few hours porting similar Java code.

I've had headaches porting perl too (though I must admit its much better now). Things these days are much better for people *trying* to develop cross-platform applications in Java and a number of other languages and APIs, but when it gets sprung on you as a requirement late in the game (latter revisions, new customers, etc) porting a Java app is a godsend.

There's alot of valid reasons to hate any language (I've studied 22 languages and in their own way, I think they all suck), but that particular reason doesn't apply to Java.